Ore on
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University
Crop Science Report
RESEARCH/ EXTENSION
KENTUCKY BLUEGRASS SEED PRODUCTION
by Harold Youngberg
1
Adaptation and Use
Bluegrass (Poo pratensis L.) is a very important and widely distributed
grass throughout the temporate zone. Kentucky bluegrass is used as coolseason turf grass because it is a long-lived perennial with wide adaptation.
Kentucky bluegrass forms a medium textured green turf of pood leaf density.
It has an aggressive sod-forming characteristic as a result of vigorous
rhizome development.
Kentucky bluegrass is capable of surviving extended
drought periods and then initiate new shoot growth from underground rhizomes
and older crowns when moisture conditions become favorable.
Kentucky bluegrass has been the standard of turf quality of many areas of
the U.S.
Newly released varieties provide improved disease resistance and
other characteristics not present in earlier varieties.
Recently releases of turf-type perennial ryegrass varieties have made
inroads on certain bluegrass uses.
However, bluegrass has many advantages
that will assure it a strong place in the market in the future.
In the past, Kentucky bluegrass was also considered an important pasture
grass in North America.
It is still often included in pasture mixtures for
parts of the humid pasture region of the eastern United States.
However,
its low mid-season forage yield, aggressiveness in mixtures, and its high
fertility requirements limit its wider use as a forage grass.
Bluegrass grown in Oregon is primarily for seed production.
Oregon produced 36% of the nation's bluegrass seed in 1980.
Linn and Marion counties
have the largest acreage with other centers of production in Jefferson, Union and Jackson counties.
Adaptation
Bluegrass is adapted to the cool, humid climate of the northern half of the
U.S.
It is found in moist, well-drained soils, growing in meadows, pastures,
fields and open woods.
It grows best on soils with a medium texture, high
fertility and a neutral pH.
1
Extension Agronomist, Oregon State University
EXT/ACS 38
8/81
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Areas of Seed Production
At the turn of the century, Kentucky produced the bulk of the Kentucky
bluegrass seed.
During the next 50 years, seed production shifted to
states west of the Mississippi River. The seed from both regions was
harvested from pastures and the annual harvest varied according to the
price.
The McCormick Seed Stripper was used in the Kentucky region and a
rotary drum-type harvester was used west of the Mississippi River. Seed
yields were not high, and care had to be exercised in curing the stripped
seed or viability and seed quality could easily be lost.
An increase of
insects and diseases in the region caused lower seed yields.
Later, development of improved varieties that could not be produced in areas of "common" type bluegrass and a demand for high quality seed caused a shift of
seed production to the Pacific Northwest states.
The development and release of Merion Kentucky bluegrass represented the
first major improvement in bluegrass.
It was first grown for seed in quantity in Oregon in the mid 1940's. The Northwestern states had the advantage
of not generally producing common bluegrass and were, therefore, free of
volunteer contamination.
Seed production practices were quite different
from those of the eastern and central regions that harvested by stripping.
The new production system resulted in higher yields, freedom from weeds,
higher viability and better seed quality.
Bluegrass seed production has now shifted to the three Pacific Northwest
states which in 1980 produced nearly all of the U.S. crop.
Annual production is, on the average, evenly divided between Oregon, Washington and
Idaho.
The demand for bluegrass seed has continued to grow.
Many new varieties
have been released by public plant breeders and more recently by private
plant breeders.
Cultural Practices
Field Selection
Proper selection of the field to be planted to bluegrass is a very important step in quality seed production. Two or three year advance planning
is necessary to control weeds and common bluegrass.
In climates and soil
where bluegrass is adapted, the seeds and plants can persist for several
Therefore, cropping patterns and herbicide
years, even under another crop.
programs during the years out of bluegrass need careful attention to avoid
contamination of the seedling field.
Annual bluegrass (Poa annua) and annual ryegrass (Lolium multiflorum) are
Perennial weeds such as
grasses that cause problems in bluegrass crops.
quackgrass (Agropyron repens) and Canada Thistle (Cirsium arvence) must be
controlled before establishing a field for seed production.
Common bluegrass in fence rows and roadsides can be sources of field conAlso, in irrigated areas, ditch banks are sources of seeds in
tamination.
irrigation water which must be dealt with.
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Soil Type
Bluegrass is adapted to soils that are moderately too well drained, medium textured with high fertility and near neutral pH. Good crops have
been grown on peat soils.
Irrigation is essential in the arid areas of
central and eastern Oregon, and may increase seed production of medium
to late maturing varieties in western Oregon.
Moderate temperatures are desirable. Reduced seed production can be expected if temperature during anthesis exceeds 90° F.
Late season frost
may damage seed set.
Stand Establishment
Bluegrass is planted in drilled rows which has several advantages. The
plantings produce higher seed yields for a greater number of years.
Weed control and roguing is easier.
In western Oregon, 12 inch wide rows
have produced higher seed yields than 30 inch rows, particularly in the
first two crops.
In irrigated areas, 6
12 inch rows are common.
Bluegrass seed is slow to germinate and root. This delay and lack of
competition with weeds during the seedling and establishment period presents a major problem in seed production.
Time of seeding is important to developing a uniform stand and rapid emergence.
When the soil is warm, bluegrass seed will germinate quite rapidly,
reducing weed competition.
Cold soils result in slower germination and reduced stand (below 42° F minimum).
Fall seedings (September 15 or later) can be expected to produce little seed
during the first season because of inadequate time for establishment and
tillering before growth stops for the winter. Therefore, spring (May or
June) plantings or mid-August to mid-September planting (with ample irrigation to obtain rapid germination) are preferred.
Bluegrass seed is very small (2.2 million/pound); therefore, seeding rates
can be quite low and still get a good stand. However, good equipment is
needed to obtain proper rate and seed placement.
Fields planted at 1-2 lbs
in 12 inch rows have produced good stands. Lower rates per acre can be used
with wider row spacing. One pound of Merlon bluegrass seed per acre in
12 inch rows will place 32 seeds per foot of drill row.
Seed should be
planted at no more than 1/4 inch depth in a smooth firm seedbed.
Irrigated in dryland areas
Irrigation is necessary when bluegrass is grown in central and eastern Oregon because bluegrass plants are fairly shallow-rooted (18 inches). Therefore, frequent irrigation is necessary to keep adequate moisture in the
effective root zone.
The frequency and amount of water to be applied at
each irrigation will depend upon the water-holding capacity of the soil in
active root zone.
Having control of moisture supply can be a very beneficial tool in managing bluegrass for seed production, as it will provide the grower some
control over growth. Since maximum seed production is dependent upon vig-
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orous tiller development in the autumn, bluegrass should be irrigated by
September 1 (in central Oregon) and kept well supplied with moisture to
keep plants in a growing condition during the autumn months.
This will
develop large tillers with stored reserves to stimulate vigorous spring
growth and reproductive tillering.
Careful management of irrigation during and after flowering is also important to maximum seed yields.
Plants should show no signs of moisture
stress until after seed maturity.
Irrigation should be continued until
near harvest.
Following harvest, irrigation should be reduced to a minimum.
Summer irrigation should be timed in conjunction with post-harvest burning to assure
that the crown is neither overly wet that the thatch will not burn, nor so
dry that severe burning of the crown damages tillers.
In some situations,
summer irrigation can be discontinued.
Fertilization
Bluegrass seed yields and plant growth respond very positively to nitrogen
fertilizer.
Best results are expected from some fall application because
of the importance of autumn growth on seed yields.
Split fall and spring
applications are most effective. Spring application of nitrogen only, tends
to produce less seed yield and result in excessive lodging.
Nitrogen rates are somewhat dependent upon the age of the stand with older
stands requiring higher rates.
Heavy nitrogen applications on older stands
will tend to overcome the tendency for lower yields as the stand ages.
Rates of 100 lbs actual nitrogen per acre split half autumn and half spring
are suggested for the first two years with 125 to 150 lbs total for the
third and later years.
Phosphorus and potassium should be used as indicated by soil tests.
TABLE 1
PHOSPHORUS AND
POTASSIUM APPLICATIONS
Soil Test
(PPm)
Phosphorus
0-15
15-30
Over 30
Potassium
0-100
Over 100
Application
(lbs/acre)
P2O5
40-60
30-40
None
K2O
60
None
(Table 1).
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Sulfur at a rate of 7-15 lbs per acre should be applied annually in western
The sulfur may be supplied in combination with the nitrogen treat-
Oregon.
ment.
Lime should be applied prior to seeding on soils with a pH below 5.8.
Weed Control
Careful field selection for freedom from weeds particularly annual bluegrass and volunteer common bluegrass is very important to seed production.
Since the primary bluegrass seed market is for high quality turf, the presence of any contaminant is very detrimental.
Weeds seeds germinate much more rapidly than bluegrass and compete strongly
with the crop, particularly during the first year.
Selection of a clean
field and care during establishment can save expensive weeding and roguing
costs at a later time.
Once established, annual weeds can be controlled by autumn and spring herbicide treatments.
(See Table 2).
TABLE 2
ANNUAL WEED CONTROL IN BLUEGRASS (WESTERN OREGON)
Chemical
Rate
Comments
Diuron
2-4 lbs
80% product
(1.6-3.2 lbs ai)
per acre
Apply in fall as soon as fall rains
start germination of weed seeds,
usually before mid-November. Spray
only well established stands.
3 lbs
Apply after first fall rains and
prior to November 1. Use IPC only
during rainy weather when soil is
moist and temperatures low.
IPC or CIPC
80% product
Ethofumestate
Nortron
1.0-1.5 lbs
ai/acre
Apply to moist soil surface after
rains start.
Terbacil sinbar
0.5-1
Apply in fall after fall rains start
germination of weed seeds and before
weeds are well established. Apply
only to well established fields
Broadleaf weeds may be controlled with 2,4-D at 0.50-0.75 lbs ai per acre
These materials are applied alone or
or Dicamba at 0.25 lbs ai per acre.
Spray applications for broadleaf control are made in the
in combination.
New spring seedings should not be sprayed before the grass has 5
spring.
leaves.
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Insect & Disease Control
Field sanitation by burning post-harvest residue or flaming fields after
straw has been removed is the most effective method for control of major
insect and disease problems.
Controls for major bluegrass insect and
disease problems are summarized in Table 3.
TABLE 3
Insect and Disease Problems in
Bluegrass in Oregon
Insect
Symptoms
Control
"Silver top"
(produced by
plant bugs)
White inflorescence
associated with
shrunken stem above
upper node; seed is
No registered chemical.
Post-harvest burning of
residue.
sterile.
Disease & Other
Rust.
Puccinia
Yellow or orange-red
pustules on leaf,
stem and panicles.
Burn stubble and straw
in the field.
Spray
plants during growing
and flowering.
See current edition of
Pacific Northwest
Plant Control Handbook.
Bluegrass varieties vary in resistance to disease.
Stem rust (Puccinia
graninis poae)and yellow strip rust (Puccinia glumarum) have caused serious
losses.
Recommended control measures are listed in Table 3.
Powdery mildew
(Erysiphe graninis) has also caused yield losses on some varieties in central
and eastern Oregon.
Disease infection can develop rapidly and result in severe losses.
must be checked frequently during the growing season.
Fields
Harvest
Varieties differ in maturity dates.
cant if harvest is delayed.
Losses from shattering can be signifi-
The crop should be swathed when the seed moisture reaches 28 percent and
allowed to cure in the windrow for 10 days before harvesting with a combine
equipped with a drapper pickup.
Combining very dry material at high cylinder speeds can result in hulling.
Care must be taken to adjust the combine to prevent losses of unthreshed
heads and spikelets. These must be returned to the cylinder for rethreshing.
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Some growers modify combines to provide a second cylinder to rethresh
In some cases, rerunning the threshed straw has been successful,
seed.
when the combine was poorly adjusted for the first run.
Seed Conditioning
Before seed conditioning, seed should be re-machined to complete the
threshing process and remove the lint or wool from the seed which will inA modified hammermill or debearder is used in the
terfere with screening.
cleaning line for this purpose.
Post Harvest Management
The care of established stands after harvest will greatly affect seed
yields in the following year. The complete removal of straw and chaff is
extremely important. This residue has some feed value (Youngberg & Vough,
Note:
Residue from
1977) particularly if baled immediately after harvest.
fields treated with pesticides should not be used for livestock feed.
Open burning of the uniformly spread straw is the most common method of
straw disposal in the seed production areas. Fields should be burned as
soon after harvest has been completed and plants under the swath have dried.
A hot fire is necessary for removal of residue and thatch that tends to build
up in older stands and cause lower seed yields.
Thatch, a zone of tightly layered dead stems, leaves, and roots intermingled
with living roots and stems developed above the soil surface as the bluegrass stand ages. Varieties differ in their tendency to develop thatch.
Thatch development of 7.2 t/A developed after one year and 55.2 t/A after
High temperfour seed crops in eastern Washington (Canode and Law, 1979).
ature open burns reduced thatch development by 50%.
The development of a thatch causes tillers to form roots within the thatch
layer rather than penetrating the soil. These plants are more subject to
They cannot take full advantage of the
injury by heat, drought, or cold.
These
soil fertility and may be subject to disease and insect injury.
weakened plants develop small tillers with inadequate stored reserves and
many remain vegetative, producing no seed.
To date, no mechanical method has been developed to reduce thatch or maintain seed yield in bluegrass other than burning.
Surface mechanical removal of residue such as crew cutting fails to affect
Mechanical tillage or renovation treatments cause severe inthe thatch.
jury to rhizomes and significantly reduce seed yields in the following
season.
Burning thins the stand providing open areas for rhizome development resulting in greater tiller development and better seed yield.
Autumn growth and tiller development is extremely important to seed yield.
Rhizome development is most rapid during warm conditions with tillers formAutumn irrigation and fertilizer timing
ing as soil temperatures decline.
should be planned to develop the optimum number of large tillers before
winter stops growth. This condition results from active plant growth favored
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by adequate nitrogen, soil moisture and open space for growth (freedom
from thatch or inter-row space).
Normal post-harvest management does not produce excessive autumn growth.
Clipping autumn growth results in reduced seed yield.
Cost and Return
An estimate of establishment and production costs for bluegrass seed production for Willamette Valley counties was made in 1979.
Costs for the
establishment year were $328.15 per acre. Based on an estimated 8-year
stand life, annual production costs were $447.10 per year or $63.85 per
100 lbs of seed, assuming a 700 lb per acre seed yield.
References
Canode, C.L. and A.G. Law, 1979. Thatch and tiller size as influenced by
residue management in Kentucky bluegrass seed production, Agronomy
Journal, 71:289-2911.
Capizzo, Joe, et al.
Pacific Northwest insect control handbook.
Revised
annually.
Available from Extension Services of Oregon State University, Washington State University, and the University of Idaho.
MacSwan, lain C., et al.
Pacific Northwest plant disease control handbook
Revised annually.
Available from Extension Services of Oregon State
University, Washington State University, and the University of Idaho.
Youngberg, Harold W. and Lester Vough, 1977. A study of the nutritive value
of Oregon grass straws, special report 473, Oregon State University
Extension Service.